1. Field of the Invention
The present invention relates to a control apparatus of a heat fixing unit of an image recording apparatus.
2. Related Background Art
Hitherto, the are a variety of image recording apparatuses in which a developing agent is pressurized with heat and is fixed by a fixing unit using a heat roller (fixing roller) having therein a halogen heater as a heating source. A temperature adjustment is executed so as to maintain a predetermined temperature by detecting a surface temperature of the heat roller.
On the other hand, the image recording apparatus of this kind use recording papers of various sizes and has a tendency toward higher and higher recording speeds. When a recording paper having a narrow width in the axial direction of the heat roller is used and the recording is successively performed, since the heat loss of a paper passing unit is larger than that of a paper non-passing unit, a temperature difference occurs between the paper passing unit and the paper non-passing unit of the heat roller. When recording is performed by using a recording paper of a wide width immediately after that, a fixing fluctuation occurs.
In order to avoid the fixing fluctuation, there is also an image recording apparatus which controls the fixing temperature so as to reduce the temperature difference by reducing a turn-on time of each heater by using two halogen heaters.
In case of executing the control in which the turn-on period is reduced by using the two halogen heaters like the above conventional apparatus, however, there are problems such that the life of a switching device is reduced by a rush current which flows at the time of turn-on of the heater and a flickering often occurs in illuminating equipment or the like connected to the same power source as that of the image recording apparatus due to the rush current.